Elimination of Electroosmotic Flow in Analytical Particle Electrophoresis

Nordt, Frank J.; Knox, Robert; Seaman, G. V. F.

doi:10.1021/bk-1976-0031.ch017

Cited by 7 publications

(18 citation statements)

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“…As shown in analytical particle electrophoresis, amine substituted agarose effectively reversed the charge of borosilicate particles. 16,17 By reversing the charge of the capillary surface using Q-agarose, wall adsorption of basic analytes is reduced by means of repulsive electrostatic forces. Furthermore, the cationic groups generate an EOF that contributes to the separation resolution by magnifying velocity differences of analytes of similar mobility, when the electrophoretic mobility is countered by the direction of the EOF.…”

Section: Resultsmentioning

confidence: 99%

Quaternary ammonium substituted agarose as surface coating for capillary electrophoresis

Ullsten

Söderberg

Folestad

et al. 2004

Analyst

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A novel positively charged polymer of quaternary ammonium substituted agarose (Q-agarose) has been synthesized and explored for use as a coating in capillary electrophoresis. The fast and simple coating procedure is based on a multi-site electrostatic interaction between the polycationic agarose polymer and the negatively charged fused-silica surface. By simply flushing fused-silica capillaries with hot polymer solution a positively charged, hydrophilic deactivation layer is achieved. The polymer surface provides an intermediate electroosmotic flow of reversed direction, over a range of pH 2-11, compared to unmodified fused-silica. The coating procedure was highly reproducible with an RSD of 4%, evaluated as the electroosmotic flow mobility for 30 capillaries prepared at 10 different occasions. The application of Q-agarose coated capillaries in separation science was investigated using a set of basic drugs and model proteins and peptides. Due to the intermediate electroosmotic flow generated, the resolution of basic drugs could be increased, compared to using bare fused-silica capillaries. Moreover, the coating enabled separation of proteins and peptides with efficiencies up to 300.000 plates m(-1).

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Section: Resultsmentioning

confidence: 99%

Quaternary ammonium substituted agarose as surface coating for capillary electrophoresis

Ullsten

Söderberg

Folestad

et al. 2004

Analyst

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“…39,40 Neutral hydrophilic polymer coatings affect the above in a complicated manner (which includes enhancing local surface viscosity, extending the plane of shear, and altering the pK's of surface groups) so as to characteristically reduce the ζ potential, that is, the electroosmosis. 1,2,[32][33][34][35]38,39 Such reduction varies directly with polymer molecular weight, grafting density, grafting chemistry, and many other factors (above references). Coating type (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Electrokinetic analysis allows for the qualitative and semiquantitative characterization of surfaces. − ,− When a charge-bearing surface is in contact with electrolyte solution, an unbalanced distribution of surface proximal ions results in the solution near the surface having a charge density (σ ≠ 0). Under an applied electric field, the surface proximal solution (ions plus hydrating water molecules) migrates in a flow, which is termed electroosmosis.…”

Section: Introductionmentioning

confidence: 99%

“…Measurement of electroosmosis by microparticle electrophoresis is sensitive to surface modifications such as the grafting density and thickness of PEG monolayers 1-3,29 (see also refs and ). Provided that the distance between the surface and the plane of shear is constant, the ζ potential (electroosmosis) is affected by the surface charge density as well as the solution viscosity, ionic strength, and other factors. , Neutral hydrophilic polymer coatings affect the above in a complicated manner (which includes enhancing local surface viscosity, extending the plane of shear, and altering the p K 's of surface groups) so as to characteristically reduce the ζ potential, that is, the electroosmosis. ,,− ,, Such reduction varies directly with polymer molecular weight, grafting density, grafting chemistry, and many other factors (above references). Coating type (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Stability of Poly(ethylene glycol) Graft Coatings

1998

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Electrokinetic surface characterization is sensitive to both charge groups (pK and surface density) and neutral polymer coatings (molecular weight, surface density, grafting chemistry). It allows nondestructive, semiquantitative evaluation of coating stability, as regards alteration of the above parameters in relation to various environments. Characterization of surface electroosmosis versus pH (2 to 11) was used to evaluate poly(ethylene glycol) (PEG) coatings of biotechnical significance following a 3-week 22 °C exposure to 0.5 M sodium phosphate solutions of pH 4-11. The coatings involved epoxide-functionalized PEGs of Mr 3400 (E-PEG 3400) covalently grafted to aminosilane-modified fused quartz capillaries. Coatings made from PEGs with an epoxide group at one end (mE-PEG 5000) were stable at pH 4-11 whereas those made from PEGs with epoxide groups at both ends (diE-PEG 3400) were only stable at pH 4-9. During storage at pH 11 the latter exhibited time-dependent generation of surface negative charge groups of pK ≈ 5.3 and surface density (≈0.1/nm 2 ) similar to the PEG grafting density. The effect was significantly reduced by N2 purging of storage solutions to remove dissolved O2 and was mimicked by fresh, carboxyl difunctionalized PEG 3400 (diSPA-PEG 3400) coatings of similar surface density. The mE-, diE-, and diSPA-based coatings studied appeared to exhibit similar grafting densities (≈0.1/nm 2 ) and coating thicknesses (7 nm), suggesting grafting at only one end group. The factors responsible for limiting surface reaction by both end groups aided the ability of the diE-PEG coatings to secondarily tether (≈0.04/nm 2 ) a model amine-containing compound (n-propylamine) at the diE-PEG-coated quartz surface. Results are discussed in relation to practical applications.

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“…The accuracy of such electrophoresis data then relies on precise knowledge of the location of this stationary plane, which is very sensitive to the geometry of the channel or capillary. Since this plane is in theory infinitely thin, EO will always contribute to some extent to the experimental error [ 16 ]. A more recent strategy is to perform mobility measurements in an alternating (AC) electric field.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the amplitude and phase of the electrophoretic and electroosmotic mobility based on fast single‐particle tracking

et al. 2021

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The electrophoretic mobility of micron-scale particles is of crucial importance in applications related to pharmacy, electronic ink displays, printing, and food technology as well as in fundamental studies in these fields. Particle mobility measurements are often limited in accuracy because they are based on ensemble averages and because a correction for electroosmosis needs to be made based on a model. Single-particle approaches are better suited for examining polydisperse samples, but existing implementations either require multiple measurements to take the effect of electroosmosis into account or are limited in accuracy by short measurement times. In this work, accurate characterization of monodisperse and polydisperse samples is achieved by measuring the electrophoretic mobility on a particle-to-particle basis while suppressing electroosmosis. Electroosmosis can be suppressed by measuring in the middle of a microchannel while applying an AC voltage with a sufficiently high frequency. An accurate measurement of the electrophoretic mobility is obtained by analyzing the oscillating particle motion for 1.5 s per particle with a highspeed camera measuring at 850 Hz, synchronized to the applied electric field. Attention is paid to take into account the effect of the rolling shutter and the non-uniform sampling in order to obtain the accurate amplitude and phase of the electrophoretic mobility. The accuracy of method is experimentally verified and compared with a commercial apparatus for polystyrene microspheres in water. The method is further demonstrated on a range of particle materials and particle sizes and for a mixture of positively and negatively charged particles.

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Elimination of Electroosmotic Flow in Analytical Particle Electrophoresis

Cited by 7 publications

References 0 publications

Quaternary ammonium substituted agarose as surface coating for capillary electrophoresis

Quaternary ammonium substituted agarose as surface coating for capillary electrophoresis

Stability of Poly(ethylene glycol) Graft Coatings

Measurement of the amplitude and phase of the electrophoretic and electroosmotic mobility based on fast single‐particle tracking

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